FDA approves third of new drugs after one clinical trial

About one-third of new drugs introduced in the U.S. from 2005 to 2012 were approved by government regulators on the basis of a single large clinical trial, according to a new study.

The wide variation in evidence behind new drugs approved by the U.S. Food and Drug Administration should be more clearly communicated to the public, according to the authors of the study, which was published Tuesday in the Journal of the American Medical Association.

"Some [drugs] are approved on very robust evidence, and some are based on preliminary evidence," Joseph S. Ross, co-author of the study and an assistant professor at Yale University School of Medicine, said in an interview. "There is a lot of nuance at the time of approval that isn't well communicated to patients."

The study identified 188 new drugs approved by the FDA from 2005 to 2012, for more than 200 uses at the time of first approval, including treatments for cancer, infections and cardiovascular disease.

The FDA approved the majority of these new uses on the basis of two or more "pivotal" trials—the industry's term for a clinical study designed to support regulatory approval—but cleared about 37% of the new uses on the basis of a single pivotal trial, the study found.

FDA guidance for drug makers typically requires at least two pivotal trials for approval, though the agency has the flexibility to make a decision on a single study, according to the study authors. Dr. Ross said scientists favor multiple studies to ensure the findings of a single study can be replicated.